The present invention relates to musical instrument tuning devices, specifically to piano tuning wrenches (also known as piano tuning hammers).
Piano tuning hammers generally consist of a lever with a wrench head on one end. The lever generally consists of a solid steel shank with a handle at the end opposite the wrench head. A typical known prior art tuning wrench is shown in FIG. 1. The wrench head of a tuning wrench includes a socket of the usual form and shape, for engagement with the tuning pins of a piano. The piano technician tunes the piano string by moving the handle of the tuning wrench while the socket is engaged upon the tuning pin as shown in FIG. 2A. This action rotates the tuning pin causing the string to wind or unwind around the tuning pin, thereby changing the string tension. The actual movement of the tuning wrench required to bring the string to proper pitch is extremely small. Accordingly, much practice and skill is required to accurately and efficiently tune an entire piano.
When the piano technician applies a force to the handle of a tuning wrench, the tuning wrench flexes as shown in FIG. 2B. When the tuning wrench deflects, it acts like a spring storing energy. Initially the tuning pin is restrained from rotation by static friction between the pin and its corresponding hole in the pin block. As the force on the tuning wrench increases, eventually the static friction is overcome and the pin begins to rotate. But when the pin begins to rotate the friction between the pin and pin block becomes sliding friction, which is less than static friction. The “wind up” that is present in deflection of the tuning wrench instantly releases and rotates the pin more than the technician intended. This results in “overshoot” and difficulty for the piano tuner to achieve accurate results.
Another known prior art tuning wrench is shown in FIG. 3. This tuning wrench has a solid steel hexagonal shank with an extendable handle. It is commonly called the “Hale extension hammer” and is widely thought to be the finest currently available, although it was developed before 1915. When adjusted to its shortest length, this type of tuning wrench may be slightly stiffer than the simple shank type of FIG. 1 due to the wood handle, but only marginally so. In addition, the telescoping feature is prone to developing movement in the sliding and gripping mechanism, thereby increasing the deflection and reducing the precision.
There have been many attempts to overcome the deficiencies of the prior art tuning hammers shown in FIG. 1 and FIG. 3. U.S. Pat. No. 610,973 to Powell (1898), U.S. Pat. No. 1,512,699 to Korach (1924), U.S. Pat. No. 2,172,355 to Brady (1939), and U.S. Pat. No. 2,751,805 to Leftly (1956) all attempt to increase the accuracy of the tuning process. A disadvantage of all four of these devices is that they all rely on an adjacent tuning pin to act as an anchor to react the torque multiplication of their gear mechanisms. This causes the anchor pin to go out of tune, which is not desirable.
Accordingly, an object of the present invention is to provide a piano tuning wrench that provides dramatically increased tuning accuracy, ease of use, and speed. This is accomplished by dramatically increased stiffness compared to the prior art. By dramatically increasing the stiffness of the wrench, the deflection is dramatically reduced and the resulting rotation of the tuning pin is more predictable.
Increased stiffness also allows the length of the wrench to be increased, allowing more increase in accuracy because the longer wrench will provide less rotation of the tuning pin for a given translation of the gripped end, resulting in greater sensitivity and tuning accuracy. The longer wrench also requires less force at the grip for a given level of torque at the tuning pin, further increasing sensitivity, accuracy, and reducing technician fatigue. Another benefit of the longer wrench and the reduced force requirement is reduced prying effect of the tuning pin. Since the handle of a tuning wrench is not in the same plane as the pin block, there will be a prying effect at the tuning pin, and consequently at the pin block. Reduction of this extra prying effect also serves to increase the predictability of the tuning process.
Very little advancement in piano tuning wrench design has been made in the past century. The best tuning hammers previously available, such as those of FIG. 1 and FIG. 3, incorporate features from patents granted in the early part of the 20th century. Considering that there is no evidence of successful advancements since that time, the elegant simplicity of the present invention is not obvious, and is novel in character.